The objective of this work is to determine the underlying biochemical and hormonal parameters responsible for normal ovarian development in mosquitoes. Our major finding thus far is the fact that the insect molting hormone, ecdysterone, is endogenously produced by adult mosquitoes and is necessary for oocyte maturation. The source of the hormone is the ovary, making it an endocrine organ, therefore paralleling the situation found in vertebrates. BIBLIOGRAPHIC REFERENCES: Fuchs, M.S. and Fong, W.F. (1976). Inhibition of blood digestion by alpha-amanitin and actinomycin D and its effect on ovarian development in "Aedes aegypti. J. Insect Physiol." in press. Fong, W.F. and Fuchs, M.S. (1976). The long term effect of alpha-amanitin on RNA synthesis in adult female "Aedes aegypti. Insect Biochemistry," in press.